This article covers some found differences and peculiarities in Android dual-SIM capability.

This information is related to device diagnostics funtionality.

IMEI and IMSI

Huawei Y6 (and possibly some other devices)

There is some variation on which IMEI and IMSI values are shown. At this time it is not known if this is the feature of Android or device.

The "primary" IMEI value readable with TelephonyManager.getDeviceId() is from the SIM card slot which was selected in Settings / Dual SIM settings / "4G/3G slot" before last reboot. I.e. reboot is needed to activate this change.

The "primary" IMSI value readable with TelephonyManager.getSubscriberId() is from the SIM card slot which is selected in Settings / Dual SIM settings / "Default calls/messages". Reboot is not needed to activate this change.

ICCID

On later Andoid devices it is possible to read ICCID of both SIM cards when the following conditions apply.

1. Device has Android 5.1 or later (API version 22 or later)
2. Device management client application has permission READ_PHONE_STATE

If user has not acceped (or has later removed) this required permission, it is not possible to read the ICCID information of either SIM.